I hear a metal expanding/ contracting sound when I put apply pressure on break when my car is on incline (More prominent when the car is on reverse on incline)

These is absolutely no sound while regular driving. Only on incline on a low speed when i apply breaks

My car is at 40,000 miles

Any ideas ?

 

I hear a creaking noise when I put apply pressure on break when my car is on incline (More prominent when the car is on reverse on incline)

These is absolutely no sound while regular driving. Only on incline on a low speed when i apply breaks

My car is at 40,000 miles and never have changed my breaks. Last break inspection was done 1 year ago and the thickness was 7 MM